Apache Performance Tuning

1. Apache Performance Tuning Part 1: Scaling Up Sander Temme <sander@temme.net>

2. http://httpd.apache.org/docs/1.3/misc/perf-tuning.html says: “Apache is a general webserver, which is designed to be correct first, and fast second. Even so, its performance is quite satisfactory. Most sites have less than 10Mbits of outgoing bandwidth, which Apache can fill using only a low end Pentium-based webserver.”

4. Performance Tuning: Goals • Serve as Many Requests as Possible • Graceful Degradation • (Don’t crash the box)

5. Assumptions • Limited Resources • Work With What You Have • You’re probably running Linux • No Compiling or Recompiling! • You can find httpd.conf

6. Monitoring Your Server

7. Purposes of Monitoring • Observation • Extrapolation • Signals/Alerts • Testing

8. Monitoring Apache

9. Monitoring Solaris: SE Toolkit • Lightweight • Programmable • Alive http://www.sunfreeware.com/setoolkit.html

10. Other Monitoring Tools • vmstat • iostat • top • free

12. Web Server Logs • ErrorLog • LogLevel: debug, info, notice, warn, error, crit • Access Log: TransferLog or CustomLog • Common Log Format

13. Common Log Format 172.16.2.91 - - [16/Nov/2003:15:23:27 -0800] "GET /~sctemme/ HTTP/1.1" 200 1446 172.16.2.91 - - [16/Nov/2003:15:23:28 -0800] "GET /~sctemme/css/doc.css HTTP/1.1" 200 167 172.16.2.91 - - [16/Nov/2003:15:23:28 -0800] "GET /~sctemme/css/menu.css HTTP/1.1" 200 623 172.16.2.91 - - [16/Nov/2003:15:23:29 -0800] "GET /favicon.ico HTTP/1.1" 404 283 172.16.2.91 - - [16/Nov/2003:15:23:34 -0800] "GET /~sctemme/index.html HTTP/1.1" 200 1446

14. Configuring for Performance • Configuring Apache • Tuning the Operating System

15. Apache Configuration • Process/Thread Management • DNS Lookups • Avoid .htaccess Files • Disable unused modules • Tune your App Tier

16. DNS Lookups • HostnameLookups • Access Control • Bad: Deny from example.com • Good: Deny from 172.160.234.5

17. .htaccess Files • Per-directory configuration files • Accessed for every request • Best performance: AllowOverride none GET /dir1/dir2/restricted.html HTTP/1.0

18. MaxClients • Configuration file directive • Maximum number of workers • Apache 1.3, 2.0 Prefork: processes • Apache 2.0 Worker: threads * processes • Limit according to resources (memory)

19. Server-side Includes • We Love Them! • Easy to implement • Easy to manage • We Hate Them! • They break sendfile() • They break cacheability

20. SSI on www.apache.org SSI Enabled

21. Sizing MaxClients • Take total RAM • Subtract OS allowance • look at free value without Apache, etc. • Subtract external program allowance • JVM, cgi programs, MySQL? • Divide by httpd process size • Read process size from top

22. Top

23. Selecting Your MPM • Apache 2.0 only! • Processes and Threads • Differences between platforms • Thread-safety issues

24. Processes and Threads • Process: • Own copy of data structures • Shares: program code, shared memory • Context switches expensive • Thread: • Runs within process • Shares process environment • No context switch

25. Platforms and Threading • Context switches expensive on Solaris, AIX • Context switches cheaper on Linux • Solaris uses M:N threading • Linux uses 1 process per thread • LinuxThreads implementation is old • Replaced by Native Posix Thread Library (NPTL) in 2.6 • NTPL already in RH 9, RHAS 3

26. Thread-safety • Third-party modules and libraries • mod_perl: experimental threading in Perl 5.6; more mature in Perl 5.8 • PHP: uses many third-party libraries • FreeBSD: threading not reliable until 5.x • Apache 2.2 Worker MPM runs on FreeBSD

27. Tune your App Tier • Tomcat • Edit server.xml, tune minProcessors, maxProcessors • Use APR -> Persistent connections • Tune JVM (Heap, Garbage Collection) • MySQL • Ships with various scenarios in support-files: • my-{small,medium,large,huge}.conf • PHP & prefork: every child makes a connection • Tune max_connections variable in my.cnf

28. System Tuning Tips • RAM and swap space • ulimit: files and processes • Turn off unused services and modules

29. RAM and Swap • Swap is disk-based Extension of RAM • Excessive swapping kills performance • Tune MaxClients • Never have more memory than swap • Upgrade RAM -> add more swap space

30. ulimit • Per-process resource limits • Built-in command of sh, bash • Important limits: • processes (-u) • open files (-n) • Set in invoking shell • Code in Apache 2.0 startup script • ulimit -S -n `ulimit -H -n` • Linux: /etc/security/limits.conf

31. Caching Content • Dynamic Content is Expensive • Static Content Relatively Cheap • Several Approaches: • Dynamic caching • Pre-rendering popular pages (index.rss…)

32. mod_cache Configuration <IfModule mod_cache.c> <IfModule mod_disk_cache.c> CacheRoot /raid1/cacheroot CacheEnable disk / # A page modified 100 min. ago will expire in 10 min. CacheLastModifiedFactor .1 # Always check again after 6 hours CacheMaxExpire 21600 </IfModule> </IfModule>

33. Make Popular Pages Static • RSS Feeds • Popular catalog queries • … (Check your access log)

34. Static Page Substitution <Directory "/home/sctemme/inst/blog/httpd/htdocs"> Options +Indexes Order allow,deny Allow from all RewriteEngine on RewriteCond %{REQUEST_FILENAME} !-f RewriteCond %{REQUEST_FILENAME} !-d RewriteRule ^(.*)$ /cgi-bin/blosxom.cgi/$1 [L,QSA] </Directory>

35. Tips • Observe Before You Act • Act on Monitoring Results • Don’t Overload Your System

36. Q&A

37. Conference Roadmap • TH9: Building a Fast and Rich Web App with PHP 5 • TH10: Troubleshooting Apache configurations • TH19: mod_perl for Speed Freaks! • TH22: Garbage collection tuning for java server processes • FR12: Getting everything out of Apache Derby database • FR1: Scaling httpd 2.x to 50,000 Concurrent Downloads • FR5: Apache Performance Tuning Part 2: Scaling Out • FR24: PHP and MySQL Best Practices 2.0

38. Current Version http://people.apache.org/~sctemme/ApconEU2006/FR4/

39. Thank You